Revealing mistake: When McClane is hanging on the steel cable which pulls their car to the river, right when he says "Run, run" there's a brief shot and it's very obvious that the guy is Bruce Willis's stunt double.
Revealing mistake: When the bomb explodes at Bonwit Tellers at the start, we see a van fly into the air. You can see the devices that throw it upwards.
Answer: And Zeus mentions about brothers knowing how to shoot guns.
He said it was racist to assume that brothers know how to shoot guns. He admitted he didn't know how to use that model.